How to add corresponding elements of 2 multidimensional matrices in python?

I have 2 multidimensional arrays , both of size 128X640X5. 5 is the number of channels for the matrices. I wish to add the respective channel values of both the matrices for every point in the matrices. For eg if we have A and B as 2 matrices, I wish to do an operation something like this:
A(x,y,0)+B(x,y,0) =A(x,y,0). This should add the 0th channel values of points x and y in both A and B and then store it back in A. Similiary I wish to do it for other 4 channels also. Any idea on how to do this in python? I am using numpy array of python and basically working on image manipulation problem.